You should be able to adjust your display by opening the Zorin menu → Settings → Devices → Displays and clicking on the “Orientation” setting to change it correctly.
If this didn’t fix the issue, the issue may be caused by your computer having a built-in orientation sensor that is sending incorrect signals, causing the screen to rotate.
After installing Zorin OS to your computer, please open the Terminal (Ctrl+Alt+T) and run the following command:
sudo apt remove iio-sensor-proxy
After running the command please reboot your computer to apply the fix.